Conventionally, for example, in an automobile equipped with a gasoline engine, a heat pump is used for cooling, while engine waste heat is used for heating. In recent years, hybrid automobiles in which the amount of engine waste heat is small, and electric automobiles in which engine waste heat cannot be used, have become increasingly widespread. Accordingly, vehicle air conditioners using a heat pump not only for cooling but also for heating have been developed. For example, Patent Literature 1 discloses a vehicle air conditioner 100 as shown in FIG. 6A.
The vehicle air conditioner 100 includes a heat pump circuit 110 through which a refrigerant flows only in one direction. The heat pump circuit 110 includes a compressor 121, a first indoor heat exchanger 131, a first expansion valve 122, an outdoor heat exchanger 133, a second expansion valve 123, and a second indoor heat exchanger 132. These devices are connected in this order by flow paths. In addition, the heat pump circuit 110 is provided with a shortcut path bypassing the first expansion valve 122, and a shortcut path bypassing the second expansion valve 123. These shortcut paths are provided with a first on-off valve 141 and a second on-off valve 142, respectively.
The first indoor heat exchanger 131 and the second indoor heat exchanger 132 are disposed in a duct 150 for selectively flowing internal air or external air. The internal air or the external air is drawn into the duct 150 from one end closer to the second indoor heat exchanger 132 by an air blower which is not shown. The internal air or the external air is blown into the vehicle interior from the other end closer to the first indoor heat exchanger 131. That is, the second indoor heat exchanger 132 is located on the windward side with respect to the first indoor heat exchanger 131.
In the duct 150, as shown in FIG. 6B, a first damper 161 is provided on the windward side with respect to the second indoor heat exchanger 132, and a second damper 162 is provided on the windward side with respect to the first indoor heat exchanger 131.
In the cooling operation of the vehicle air conditioner 100 having the above configuration, the first on-off valve 141 is opened, and the second on-off valve 142 is closed. In addition, the first damper 161 and the second damper 162 are set at positions shown by solid lines in FIG. 6B. Therefore, the refrigerant discharged from the compressor 121 flows into the outdoor heat exchanger 133 without releasing heat in the first indoor heat exchanger 131, releases heat in the outdoor heat exchanger 133, and is then expanded by the second expansion valve 123. The expanded refrigerant absorbs heat in the second indoor heat exchanger 132, and is then drawn into the compressor 121.
On the other hand, in the heating operation, the first on-off valve 141 is closed, and the second on-off valve 142 is opened. In addition, the first damper 161 and the second damper 162 are set at positions shown by chain double-dashed lines in FIG. 6B. Therefore, the refrigerant discharged from the compressor 121 releases heat in the first indoor heat exchanger 131, and is expanded by the first expansion valve 122. The expanded refrigerant flows into the outdoor heat exchanger 133, absorbs heat in the outdoor heat exchanger 133, and is then drawn into the compressor 121 without further absorbing heat in the second indoor heat exchanger 132.